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McDonnell XF-85 Goblin

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XF-85 Goblin
Small egg-shaped aircraft with three vertical stabilizers, resting on yellow movable rig
XF-85 serial number 46-523 in the National Museum of the United States Air Force
Role Parasite fighter
Manufacturer McDonnell Aircraft
First flight 23 August 1948
Status Canceled, 1949
Number built 2

The McDonnell XF-85 Goblin was a prototype fighter aircraft, conceived during World War II by McDonnell Aircraft. It was intended to be carried in the bomb bay of the giant Convair B-36 "Peacemaker" bomber as a defensive "parasite fighter". During World War II, Luftwaffe fighters provided stiff opposition for Allied bombers. The XF-85 was a response to a United States Army Air Forces (USAAF) requirement for a parasite fighter capable of being carried within the Northrop XB-35 and B-36 then underdevelopment. Two prototypes were built, which underwent testing and evaluation in 1948. Flight tests showed promise in the design, although the aircraft's inherent design flaws associated with parasite fighters were never resolved. It was swiftly canceled due to a number of factors, and are now museum exhibits.

Design and development

At the end of World War II, Luftwaffe fighter jets posed a danger to Allied bombers which were making their offensive bombing runs. This emphasized the importance of long-range escort fighters, such as the P-47 Thunderbolt and P-51 Mustang. However, the United States Army Air Force (USAAF) was developing bombers, namely the Northrop B-35 flying wing and Convair B-36, which had a much longer endurance than the B-17s, B-24s and B-29s the fighter escorts were protecting at the time. There were a number of options to protect the bombers. The first, developing longer-ranged fighters, was very expensive. The second option was the technically-risky aerial refueling. The last was to develop a parasite fighter, or an "internally stowed fighter".[1]

In the 1930s, the U.S. Navy had been testing the viability of such aircraft, constructing the USS Akron and Mason for scouting, as well as launching the Curtiss F9C Sparrowhawk.[2] In January 1944, the Air Technical Service Command (ATSC) began looking for a solution to combat the opposition from the Luftwaffe. By January 1945, it was decided that the best option was to develop a parasite fighter.[2] The USAAF, meanwhile, asked a number of aerospace companies regarding the feasibility of such aircraft; McDonnell was the only company which submitted a proposal.[2]

Black-and-white top view of egg-shaped aircraft, with a hook extended on top of canopy
Top view of the XF-85, with the hook extended on top of the canopy

The Model 27 initial concept was to be carried half exposed under the B-29, B-35 or B-36. The USAAF, however, rejected this, citing increased drag, and hence reduced range for the composite bomber-fighter configuration.[2] On 19 March 1945, a revised proposal was submitted. The smaller aircraft had an egg-shaped fuselage, three fork-shaped vertical stabilizers, horizontal stabilizers with significant dihedral, as well as 37° swept-back wings. The miniature aircraft measured 14 ft 10 in (4.55 m) long, the folding wings spanned 21 ft (6.4 m), and had a empty weight just short of 4,000 pounds (1.8 t).[3] To save weight, the parasite fighter had no landing gear. During the testing program, steel skids were installed in case of any emergency.[2][4] Four .50-caliber machine guns made up the aircraft's armament.[5]

In service, the parasite fighter would be launched and retrieved by a trapeze system. The aircraft would approach the mother ship from underneath, and with a retractable hook on top of the cockpit, would link up with the trapeze. The 24th B-36 onward were to be built to accept one parasite fighter, with a maximum of three per bomber envisioned.[5]

On 9 October 1945, the USAAF signed a contract for two prototypes (US serial numbers 46-523/4), although the contract was not finalized until February 1947.[6] Model 27 was re-designated "XP-85", but by June 1948, was changed to XF-85 and given the name "Goblin".[5] There were plans to acquire 30 production P-85s, but the USAAF took the cautious approach – if test results from the two prototypes were positive, production orders for the Goblins would be later finalized.[6] During wind tunnel testing at Moffett Field, California, the first prototype XF-85 was damaged. Consequently, the second aircraft was used for the initial flight tests.[7]

Operational history

As the B-36 was unavailable, all XF-85 flight tests were carried out using a converted EB-29 Superfortress parent ship. Since the B-29, named Monstro, was smaller than the B-36, the XF-85 would be flight-tested half-exposed.[7] On 23 August 1948, the XF-85 flew the first of several captive flights, designed to test whether the EB-29 and its parasite fighter could fly "mated".[4]

Although in flight, the fighter was stable, easy to fly and recovered well from spins, initial estimates of a 648 mph (1,043 km/h) top speed proved optimistic.[7] McDonnell test pilot Edwin Schoch, who flew the only proving flights on the type, also found it difficult to hook the Goblin to the bomber's trapeze. Even after Schoch had flown dummy dockings with a Lockheed F-80 without problems, the lighter Goblin proved to be more sensitive to turbulence than the F-80. On 28 August 1948, his fourth flight aboard the EB-29 mothership, and the first "free" flight, Schoch was released, attempted a hook-up, but it became obvious that turbulence around the bomber created difficult control problems. In an aborted effort, Schoch struck the trapeze so violently that the canopy was smashed and his helmet and mask were knocked off. He saved the prototype by making a belly landing.[8] Schoch was able to make a successful hookup on 14 October 1948, [9]and although McDonnell considered adding a telescoping extension to the docking trapeze, before modifications could be carried out, the USAF canceled the XF-85 program on 24 October 1949.[10]

The program was canceled not only because the XF-85's performance proved inferior to contemporary foreign jet fighters but also due to the high pilot demands involved should the XF-85 fail to dock, as evidenced by the test program flights. The development of practical aerial refueling was also a factor in the program cancellation.[7][4] The Goblin flew six times with a total flight time of 2 hours and 19 minutes;[7] Schoch was the only person who ever flew it.[11]

Aircraft on display

Two XF-85 prototypes were built, and both still survive:

Specifications (XF-85)

Black-and-white photograph of small egg-shaped fighter aircraft hoisted by a lifting mechanism underneath a large bomber.
Hangar test of recovery trapeze, with wings folded in stowed configuration.

Data from Experimental & Prototype U.S. Air Force Jet Fighters,[13] Boeing,[4] National Museum of the United States Air Force,[14]

General characteristics

  • Crew: 1

Performance

Armament

See also

Related lists

References

Notes
  1. ^ Jenkins and Landis 2008, pp. 80–81.
  2. ^ a b c d e Jenkins and Landis 2008, p. 81.
  3. ^ Winchester 2005, p. 151.
  4. ^ a b c d "McDonnell XF-85 Goblin Parasite Fighter." Boeing. Retrieved: 29 June 2011.
  5. ^ a b c Jenkins and Landis 2008, pp. 82–83.
  6. ^ a b Jenkins and Landis 2008, p. 82.
  7. ^ a b c d e f g Jenkins and Landis 2008, p. 85.
  8. ^ Gunston 1981, pp. 127–128.
  9. ^ Gunston 1981, p. 128.
  10. ^ Yeager and Janos 1986, p. 179.
  11. ^ Dorr 1997, p. 101.
  12. ^ United States Air Force Museum Guidebook 1975, p. 76.
  13. ^ Jenkins and Landis 2008, pp. 81–82.
  14. ^ "McDonnell XF-85 Goblin." Nationalmuseum.af.mil, 18 March 2010. Retrieved: 29 June 2011.
Bibliography
  • Dorr, Robert F. "Beyond the Frontiers: McDonnell XF-85 Goblin — The Built-in Fighter." Wings Of Fame, Volume 7, 1997.
  • Gunston, Bill. "McDonnell XF-85 Goblin." Fighters of the Fifties. North Branch, Minnesota: Specialty Press, 1981. ISBN 0-93342-432-9.
  • Jenkins, Dennis R. and Tony R. Landis. Experimental & Prototype U.S. Air Force Jet Fighters. North Branch, Minnesota: Specialty Press, 2008. ISBN 978-1-58007-111-6.
  • Knaack, Marcelle Size. Encyclopedia of US Air Force Aircraft and Missile Systems: Volume 1 Post-World War II Fighters 1945-1973. Washington, DC: Office of Air Force History, 1978. ISBN 0-912799-59-5.
  • Yeager, Chuck and Leo Janos. Yeager: An Autobiography. New York: Bantam Books, 1986. ISBN 0-553-25674-2.
  • United States Air Force Museum Guidebook. Wright-Patterson Air Force Base, Dayton, Ohio: Air Force Association, 1975 edition.
  • Winchester, Jim. "McDonnell XF-85 Goblin". Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft. San Diego, US: Thunder Bay Press, 2005. ISBN 1-59223-480-1.
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